This invention relates to a power transmission chain belt and, in particular, to a power transmission chain belt for use with a continuously variable transmission (CVT). More particularly, the present invention relates to a chain belt for a CVT with an asymmetrical guide link and a modified strut and link geometry that places the strut closer to the pitch line of the chain.
The belt of the present invention is comprised of a large number of interleaved link plates which are placed parallel to the chain width direction and carry a number of load blocks or struts for transmission of power to the variable width pulleys of the CVT. The belt is formed of a plurality of adjacent chain portions that are offset or phased by a portion of one chain pitch. Preferably, the belt is formed of at least two adjacent chain portions that are offset or phased by one-half pitch.
An example of a power transmission chain belt as used in a CVT is shown in FIG. 1 of the drawings. As shown in that figure, the CVT includes input shaft 101a and output shaft 102a, which carry primary (drive) and secondary (driven) pulleys 103a, 104a, respectively. The chain belt 105a interconnects the primary and secondary pulleys of the CVT.
Primary pulley 103a includes fixed pulley portion 103a', which is fixed to input shaft 101a, and moveable pulley 103b', which is moveable along input shaft 101a. Similarly, secondary pulley 104a includes fixed pulley 104a', which is fixed to the output shaft 102a and moveable pulley 104b', which is moveable along the output shaft. The effective diameters of pulleys 103a and 104a are changed by movement of the moveable pulley portions 103b', 104b', which is caused by operation of hydraulic actuators, as is known in the art. In this manner the speed change ratio between the input and output shafts can be varied continuously.
FIG. 2 generally illustrates a sectional view of a portion of a chain of the prior art for use in a variable pulley transmission of the type schematically illustrated in U.S. Pat. No. 5,007,883, which is incorporated herein by reference. The chain 10 comprises two chain assemblies or two chain portions 12, 14. The two portions 12, 14 are disposed in side-by-side relationship with the chain portions being offset from one another by one-half pitch. That is, the first chain 12 and second chain 14 are offset from each other by one-half pitch.
The two chain portions are interleaved and connected by pairs of pivot pins 16, 18 that extend through apertures in each of the links. One pin 16 is longer than the other pin 18 and extends through a guide link on the outside of the chain, as explained in more detail below.
The first portion of the chain includes a plurality of rows or sets 20, 22 of interleaved inner links 41. The inner links 41, shown more clearly in FIG. 8, are interlaced so that the apertures 48, 50 of one link set are transversely aligned with the apertures of the links of the next adjacent set. In this way, the rows of links articulate with respect to one another. The inner links include a pair of depending toes 42, 44 that extend downwardly from the link body. The toes define a passageway 45 for the retention of a strut 11, which is explained in more detail below.
The first portion of the chain of the prior art as shown in FIG. 2 includes retaining links 47 on alternate rows of the chain. The rows with retaining links include five links across each row. That is, three inner links with a retaining link on each outside. Retaining links are present in prior art chain assemblies to restrict excessive lateral motion of the strut. The retaining links are located on the ends of the link rows not containing guide links. The link passageway is shaped to restrict excessive lateral motion of the struts in the adjacent row. The rows without retaining links include four inner links across the width of the chain. Guide links 24, 36 are placed outside the retention links.
The inner links and retaining links include pairs of apertures that permit pairs of pins to extend through each aperture. The guide links include pairs of apertures that permit only a single pin to extend through each aperture. The single pin is fit securely in the aperture of the guide link and does not rotate with respect to the guide link. The pairs of pins in each aperture of the inner links rotate or rock with respect to one another, which permits the articulating motion of the inner links and rows of interleaved inner links. The use of rocker joints and pins in apertures of CVT chains as well as silent chains is well-known in the art. A pin and rocker joint is shown in U.S. Pat. No. 4,507,106, which is incorporated herein by reference. Pairs of pivot members extend across the length of the first portion of the chain and terminate slightly beyond the ends of the retaining members.
The second chain, or other chain portion, of the chain belt is also comprised of a plurality of interleaved inner links. The inner links are interlaced so that the apertures of one link set are transversely aligned with the apertures of the next adjacent set. In this way, the rows of links articulate with respect to one another.
The second portion of the chain also includes retaining links on alternate rows of the chain. The rows with retaining links include five links across each row. That is, three inner links with a retaining link on each outside. The rows without retaining links include four inner links across the width of the chain. The inner links in the second portion of the chain act in a similar manner to the inner links in the other portion of the chain. The links also include pivot members and rocker joints, in the same manner as the first portion of the chain.
Referring to FIG. 3, a long outboard load block or strut is held in the passageways formed between the depending toes of the links to engage the flanges of the pulleys. The strut 11 is symmetrical about a vertical centerline in the end direction and in the lengthwise (or transverse) direction. The strut includes a top 80, two rounded link contacting surfaces 82, 84, two grooves 86,88, a first side 90, a second side 92, and a bottom 94. The upper region of the strut, including the top and the rounded contacting surface, is similar in shape to the passageway and is only slightly smaller in size to allow the strut to be positioned in the passageway of the link.
In FIG. 4, a front view of the strut 11 shown in FIG. 3, the top of the strut includes an upper portion 80a and an extending portion 80b and ends 96, 98 that contact the flanges of the pulleys.
FIG. 5 illustrates a guide link 36 of the prior art. The link 36 has a pair of apertures 148, 150 for receiving the pins of an associated rocker joint pivot member. The apertures, and link configuration, is generally symmetrical about a vertical centerline. The link comprises a top 130, preferably substantially horizontal, and a bottom having two spaced depending toes 142, 144 that define a passageway 100 for the upper portion of a strut. The depending toes are shaped to hold the strut within the passageway 100.
FIG. 6 illustrates the aperture 150 in more detail. The aperture includes upper and lower curved portions 152, 154. The back portion 156 is preferably slightly curved to permit the pin to seat against the back portion. The front portion 158 is also curved at a radius that matches the radius of the rocker pin. A rocker pin is fit securely into the aperture 150.
FIG. 7 illustrates the passageway 100a of the link in more detail. In FIG. 7, the passageway has rounded inner portions 102, 104 and a rounded upper portion 105. The rounded inner portions form two toes 106, 108 at the bottom of the link. The upper portion of the strut is shaped to match the upper portion 105 and inner portions 102, 104 of the link.
FIG. 8 illustrates inner link 41 having a substantially flat or horizontal top portion 43. The top portion 53 of the passageway 45 is curved to match the strut. Sides 46, 49 angle from the top 43 to join the toes 42, 44.
The aperture 159 of an inside link is shown in detail in FIG. 9. The aperture includes a slightly rounded back portion 162 and a fully rounded front portion 164. Additionally, top portion 166 and bottom portion 168 are rounded. A pair of rocker pins are typically utilized that have curved front portions that engage each other with rocking contact.
An alternative link passageway of the prior art is shown in FIG. 10. The passageway 200 includes inside rounded portions 202, 204, that form toes 206, 208. The upper portion 210 of the passageway is formed into another rounded portion to provide greater retention of the complementary strut in the passageway.
Examples of phased transmission chains for CVTs are shown in U.S. Pat. Nos. 5,645,502 and 5,453,058, which are incorporated herein by reference. When these transmission chains are used, noise is generated as the load blocks or struts contact the sides of the pulleys. Efforts have been directed to decreasing the noise generated during such contact while maintaining a durable chain. Efforts at decreasing noise generation and minimizing the number and complexity of chain components involved, for example, using links of more than one pitch length, alternating the lengths of the struts, and changing the length of the windows of the links that receive the struts.
Other efforts at noise reduction in the prior art have included the use of two chain portions positioned in side-by-side relationship, but offset or phased by one-half pitch length. Other phased chains of the prior art have utilized three chain portions positioned in side-by-side relationship, but with the center portion offset from the two outside chain portions by a distance of one-half pitch length. The chain of the present invention is directed to phased chain with two chain portions.